The present invention relates to a process for preventing polymer agglomeration and for controlling the density of copolymer produced by an alpha-olefin copolymerization process in a polymerization reactor, wherein the ratio of the flow rates of introduction of the comonomer(s) to the monomer is kept constant.
It is well known to copolymerize olefins, for example ethylene, propylene, butene, hexene and octene, continuously, for example in the gas phase in a fluidized-bed or mechanically stirred reactor in the presence of a polymerization catalyst, for example a Ziegler-Natta-type catalyst, a metallocene, a chromium catalyst, an iron or cobalt catalyst.
Numerous methods have already been described in the literature in relation to controlling the polymerization reaction. When carrying out the copolymerization of alpha-olefins in a polymerization reactor in the presence of a metallocene catalyst, the Applicant was unable, using known methods, to simultaneously control effectively the density of the copolymer produced and to prevent polymer agglomeration, as borne out by the comparative example described hereinbelow.
Unexpectedly, the Applicant has found that the density of a copolymer produced by continuous gas phase polymerization in the presence of a metallocene catalyst can be effectively controlled and that polymer agglomeration can be effectively prevented by keeping constant the ratio of the flow rates of introduction of the comonomer(s) to the monomer.